Building A Passive Headphone Mixer

BeniRose

BeniRose

New member
Hey there guys! I have an ambitious project that I might need some help with. I'd like to build myself a passive headphone mixer/control room matrix. Basically, it's just 4 stereo inputs and 4 stereo outputs that pretty much route straight through, but with the addition of certain things on each channel. Here's a mock up of the signal flow:

CueMixer.jpg


Sorry if that's a little confusing. Basically, there's 4 channels. A star denotes signals mixing together. The main inputs (Out 1-2 from my Saffire) are for the room monitors. There are two headphone monitoring channels (Out 3-4 and 5-6) that will go to their own sets of outputs, after being mixed in with a talkback mic (which needs a momentary switch on it) and mixed with the Aux in, which is the 4th channel. The aux in will also mix into the main inputs/outputs. After mixing with the aux, the mains will then go to a volume control with mute, dim, and mono buttons. After these controls, it will get split into highs and lows and go to two seperate Monitor and Sub outputs. This is more of a nice to have, so I might leave it out in my first design. I don't even have a sub at the moment anyways. Lastly there will be a second pathway from the main inputs before the controls that gets mixed in with the talkback mic and goes to a cue output, which will go into my headphone amp on my rack. It's essentially the main mix with talkback in it. I'm not even sure I would need the power, because ideally this whole thing is passive.

So here's the problem. I can solder till the cows come home, but I really don't know too much about electronics. I'm not sure how to wire things up, and most importantly, I don't know what components I need. I'm assuming it'd mostly be resistors, potentiometers, momentary switches, 1/4" jacks, and a cheap mic capsule but I'm really not sure what kind I need or how exactly to wire them up.

Would anyone be willing to help me out? Maybe draw up some schematics a noob could read with a parts list? I will love you forever!!
 
For $49 and free shipping, you can buy a half-decent one; Samson S-Amp | Sweetwater.com.
But if you have to make one yourself, passive has its drawbacks. Each set of headphones will lower the effective impedance, and eventually you load down the input signal. But it can be done if you can tolerate less than stellar fidelity.
Altoids Tin 1/8" Stereo Mixer.
I still say $49 for an active mixer is the 'better' way to go, even at this entry level quality.
 
Hey Ranjam. Thanks for the reply. I actually have owned an S-Amp before and own two Rolls headphone amps similar to that one, but that's not what I'm going for here. It's not a headphone amp in the sense that it's taking one signal and distributing the same signal to multiple outputs. It has 4 inputs that pass of to 4 outputs (really 3 inputs/outputs and an aux in). They don't really mix with each other, most of them mix with either the talkback mic or the aux-in. That's why I thought it should be passive, because at most I'm mixing two signals together, and really the point is to attenuate the signal with a pot (volume control). I'm not against it being powered, I just thought there was no need, as everything is getting amplified by either a powered headphone mixer or amp (monitors) after it comes out of the outputs. Thanks for your suggestions though.
 
Any progress on this? It sounds very interesting. Wouldn't the talkback mic need some amplification? I've thought about using a small mixer to do something similar, but there has to be an easier way.
 
There are reasons why Passive mixers aren"t common and more popular , and that reason is they Suck ......

When Mixing you have to use Resistors to sum inputs and Pots to controll levels and all of this introduces Losses of signal and change of impedance which also increases losses so what comes out of the mixer isn"t going to sound the same as what is going in , most likely sound like shit and at a low volume ......

The way to overcome the losses is to buffer the incoming signals there by keeping the signal impedance low and to add an output stage with gain to to overcome and losses caused by summing .......

active is the way to go but it can also be battery powered so it is portable ....... it is a lot of work for something that is way to cheaper to buy than to build ......
 
Thanks Minion. I haven't found anything I can buy that provides what I'm looking for (basically mixing a talk-back mic into 4 stereo channels, think of it like 4 two channel mixers in one box, with a volume pot on just one of those stereo channels) and anything that gets close is VERY expensive. That's why I thought I'd try to build it. Maybe I could mod a cheap mixer to do what I want.
 
750-SplitMix4_back.jpg


Think of it like this ART passive mixer, except instead of the mixing/splitting going across horizontally, each channel just passes through the feed vertically, with a talkback mic getting mixed into all 4 channels.
 
In fact, it looks like it already does that, except when I plug cables into the output jacks on the top, it disables the input jack on the top. If I could figure out a way to keep that from disabling, I could plug a talk-back mic into that top input jack and it will combine that signal with the input jacks in the bottom row. I wonder if this is possible.
 
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